Ceramics-Silikáty 50 (3) 178-184 (2006)

THE STUDY OF NEUTRALIZATION OF THE DIHYDRATE PHOSPHOGYPSUM IMPURITIES

A. Kaziliunas, V. Leskeviciene, B. Vektaris, Z. Valancius

The paper presents the characterization of dihydrate phosphogypsum impurities, both in laboratory and in industrial scale, and chemical process of their neutralization in the lime suspension. The fastest and controlling processes of transfer water soluble impurities to insoluble compounds of calcium orthophosphates {Ca₃(PO₄)₂ •nH₂O and Ca₅(PO₄)₃OH•mH₂O}, CaF₂, CaSiF₆, Ce(OH)₃ were determined. The impurities in the phosphogypsum crystals were neutralized under hydrothermal conditions (in an autoclave). The increased quantity of alkalies in the recycling water did not have influence on the phosphogypsum neutralization process and on the properties of the plaster made from phoshpogypsum. Neutralized phosphogypsum may be used in the production of gypsum binding materials.

Keywords: Phosphogypsum, Impurities, Neutralization, Properties, Binding materials